# The physics of Rugby

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• Created on: 20-12-12 18:39
• The Physics of Rugby
• Work is done when energy is transfered from one form to another
• the unit of work is a joule (J)
• the equation for work done is: force used (N) x distance moved in the direction of the force (m)
• There is always a proportion of energy lost as heat/ sound when energy is transferred from one form to another
• human muscles are about 25% efficient i.e. 75% energy is wasted as heat rather than kinetic energy
• the equation to find the kinetic energy of a moving object is KE = 0.5mv^2
• for objects moving through the air in an upwards direction,their kinetic energy will gradually change to gravitational potential energy as the object does work against gravity
• the object will start to slow down as it has less kinetic energy
• PE (gravitational potential energy) = mass(kg)x gravitational strength(g) x change in height(m)
• when all the kinetic energy of the object has converted to gravitational potential energy+ the vertical velocity is zero- the object starts to fall
• the potential energy starts to convert back to kinetic energy
• during the object's movement, the total energy remains constant (kinetic energy + potential energy)
• Newton's third law says:"In an interaction between two objects (A+B) the force exerted on A by B is equal+ oppositely directed to the force exerted on B by A
• Together the action force and the reaction force make an interaction pair
• 'Contact forces' are where the objects must have contact to exert the force/ may be 'action at a distance' forces like gravity/ electromagnetic forces